In the development and production of subterranean hydrocarbon deposits and other energy sources there are many occasions when it is necessary to insert an elongated tube from the surface deep into a pipe or open hole. Such pipes or holes may be vertical, horizontal, curved or combinations thereof and may be part of, for example, a well, pipe line, production line, or drill pipe. The inserted tube has an outer diameter that is smaller than the inner diameter of the pipe or open hole. The insertion of the tube may be for such purposes as, for example, removing blockages or general servicing.
Often during repair or servicing of a pipe a rig capable of handling long lengths of straight screw-type pipes is not available. In many cases the strength of larger diameter straight screwed tubing is not needed, so the cost of running this type of tube is not justifiable. In these cases it is often advantageous to use a long, continuous injected tubing called coiled tubing. Many apparatus have been developed to insert or inject a continuous length of relatively thin walled steel tubing into a pipe or open hole from a large reel or spool on the surface.
Large forces are often necessary to insert and withdraw thousands of feet or more of steel tubing into a pipe or open hole which may be filled with hydrocarbons or other materials. Most apparatuses developed heretofore have focused on the injector head located where the smaller tubing is injected into the larger tubing. The injector head grips the tubing along its length and, in conjunction with a motor, guides and forces the tubing into the pipe via, for example, a dual, opposed conveyor belt on the surface of the well. Typical injector heads are described in, for example, U.S. Pat. No. 3,827,487; 5,309,990; 4,585,061; 5,566,764; and 5,188,174 which are incorporated herein by reference.
Unfortunately, the apparatuses of these patents are problematic in many respects. One such problem is that the tubing may be bent or kinked, i.e., the tubing becomes helical, down the well due to the large forces pushing against it and the weight of the tubing itself. This is especially problematic when the pipe is deviated from vertical. As the pipe becomes more horizontal, the weight of the coiled tubing itself no longer acts as a force pulling the tubing along, and instead acts against the wall of the pipe, creating friction. In addition, the weight of the tube no longer acts to straighten the coiled tubing, and the coil encourages coiling in the pipe. Such a coil, coupled with friction, results in increased force between the coiled tube and the inner diameter of the pipe, and this effectively binds the tubing. As a result of this and other problems, such prior art devices cannot effectively insert more than about 3,000 to about 5,000 feet (900 to 1500 meters) of tubing in substantially horizontal pipe.
Another typical problem with prior art devices is that the injector equipment associated with such devices is often relatively heavy, difficult to move, and complex due to a large chain assembly machinery which serves as a conveyor belt to force the tubing into the pipe.
Other methods have been employed to increase the length to which tubing can be injected. U.S. Pat. No. 5,704,393 describes an apparatus that can be set in the well at the end of the coiled tubing string at a determinable location. The apparatus is a valve apparatus, a packer apparatus, and a connector. Seals are provided which allows the coiled tubing, but not fluid, to move in a centrally located bore through the packer apparatus. The apparatus is immobile against the outer pipeline, and has the ability restrict or prevent fluid flow. Once the packer is set, the annular pressure , i.e., the pressure differential between the pipeline and the interior of the coiled tubing, is increased by injecting fluid into the annular volume. This increased pressure stiffens and straightens the coiled tubing, allowing for increased distance of injection of coiled tubing into the pipeline.
One method of reducing friction in injected tubing is the tubing friction reducer described in U.S. Pat. No. 5,692,563. This patent describes a friction reducer that contains multiple bearings set in legs that extend outward from a body. The friction reducers described by the patent did not have the mechanical integrity needed to support the weight of larger diameter tubing. Applicant also found that the design of the friction reducers described therein could not be used in field conditions where obstructions in the pipeline are common.
It is apparent that what is needed in the art is a method and apparatus which allows one to readily insert and withdraw tubing from a pipe for long distances, i.e., greater than about 6,000 feet (1830 meters), without bending or kinking the tubing. It would be beneficial if such a method and apparatus could be employed to insert and withdraw tubing from a substantially horizontal pipe of extended length of greater than 6,000 feet (1830 meters), and that the tubing can extend past turns. Moreover, it would be of great benefit if such an apparatus was portable, easily handled, and could be adapted to handle tubing of differing diameters.